The formation of a recess in a blow molded article, wherein said recess is located proximal to an opening portion of the article, is highly desirable as it enables the integration of the design of the closure with the design of the article. This integration in turn allows the manufacturer to form consumer pleasing designs whilst making closure functioning intuitive to the user. More desirable still is the integration of the closure with the article such that the closure can be miniaturized. This miniaturization of the closure is desired as it reduces the weight of the closure thus reducing the amount of raw material and energy consumed. A further advantage is that stability of the article may be attained in both top side up and inverted positions, this thanks to the flat surface generated by article and closure.
The manufacture of a blown article comprising at least one recess, wherein said recess is located proximal to an opening portion of the article, is technically challenging. This is because the formation of a recessed neck requires the article to form a shoulder(s) above the top portion of the neck portion. This is technically challenging because the material flow to form such shoulders would be against the natural material flow in blow molding. The natural material flow in blow molding is from the neck of the parison or preform towards the base of the article guided by a pressure build up that expands the walls of said article being formed to the shape of the mold cavity. Moving material against that natural flow direction requires careful design of the parison or preform, and careful definition of the blowing process.
Another challenge is that, such shoulder being above the neck, generates undercuts during the blow molding process which prevents the unmolding the finished article when using known unmolding processes. This is particularly true if such shoulder presents multiple curves on its surface. One cannot unmold an article with such undercuts without damaging the article.
The art contains a number of attempts to solve the inherent problems of forming recessed blow molded articles.
One approach has been to form containers having recesses that do not generate undercuts, such as those described in USD573469 (The Procter & Gamble Company). Such recesses allow unmolding with a simple “straight-pull” action from a standard mold. However, such recessed geometries that can be unmolded with a straight pull in a blow mold are highly restrictive in terms of design of the recess geometry that may be obtained. This in turn limits the degree of integration of the closure with the blown article and thus fails to attain the above stated benefits.
Another approach has been to blow mold the article in a mold cavity followed by a second step of trimming (or deflashing) the excess plastic in order to finish the geometry of the recess. An example of this approach is described in U.S. Pat. No. 6,357,625 (OWENS-BROCKWAYS PLASTIC PRODUCTS). However, a number of disadvantages arise with the use of such a process which become apparent to the person skilled in the art. Firstly, the operation of trimming excess material is inherently cost ineffective and should thus be avoided. Secondly, any trimming operation requires complete access to the portion that is to be trimmed, thus restricting the recess geometry that may be obtained. Thirdly, such restriction of the recess geometry limits the integration of the closure with the blown article and thus also fails to attain the above stated desired benefits.
It is an objective of the present invention to provide a process for the production of a blow molded article, comprising a recess that integrates, at least with part, of the closure, such that the closure, when coupled with the blown article, may be substantially flush to the apex of the outmost surface of said article.
It is another objective of the present invention to provide a blow molding process forming a recess in the blown article, such that at least a portion of said article wraps around at least a part of a closure when coupled to the blown article.
It is a further objective of the present invention to simplify the de-molding of articles comprising undercuts proximal to the neck portion thereof, whilst preventing damage to the article during such operation.